6. Potentiometer

The examples below use sequence without definition blocks which are preferred to better organize the code.

See https://pc-microbit-micropython.readthedocs.io/en/latest/breadboards/Potentiometer_2.html

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The potentiometer is a variable resistor.

Turn it one way to reduce the resistance. Turn it the other way to increase it.

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6.1. Model

1. Place the potentiometer.

2. Connect with the jumper wires.

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6.2. Read analog

To read the value of the potentiometer use pin2.read_analog.

The code below reads the value and displays it.

Try turning it from side to side to see the effect.

from microbit import *

while True:
    pot_val = pin2.read_analog()
    display.scroll(pot_val, delay=80)
    sleep(20)

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6.3. Scaling potentiometer readings

scale(value, from_, to)

Converts a value from a range to another range.

Parameters:

• value – A number to convert.

• from – A tuple to define the range to convert from.

• to – A tuple to define the range to convert to.

Returns:

The value converted to the to range.

e.g. temp_fahrenheit = scale(30, from_=(0.0, 100.0), to=(32.0, 212.0))

Tasks

1. Modify the code to scale the potentiometer value in the range 0 to 9 and scrolls its value.

Q1

Modify the code to scale the potentiometer value in the range 0 to 9 and scrolls its value.

from microbit import *

while True:
    pot_val = pin2.read_analog()
    scaled_pot_val = scale(pot_val, from_=(0.0, 1023.0), to=(0, 9))
    display.scroll(scaled_pot_val, delay=80)
    sleep(20)

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6.4. EXT: Demo: Power meter simulation

The code below takes an analog value from the potentiometer and displays it on the microbit LEDs.

See the custom images lesson for more on display.set_pixel.

The maximum potentiometer reading is 1023, so this can be treated as 1000 for simplicity.

This gives 5 levels in steps of 200.

from microbit import *

while True:
    level = pin2.read_analog()
    val = int((level % 200) * 9 / 200)

    # Determine row position for the bar
    y_val = max(0, 4 - (level // 50)) if level > 0 else 5

    # Update display pixels
    for x in range(5):
        if y_val < 5:
            display.set_pixel(x, y_val, val)  # Set active pixel brightness
        for y in range(5):
            display.set_pixel(x, y, 9 if y >= y_val else 0)  # Set other pixels

    sleep(20)